The present invention relates to thin-walled bearing bushings produced by a drawing process particularly adapted for the support pins in universal joints. The bearing bushing consists of a cylindrical sleeve section and a bottom section which closes the cylindrical sleeve section on one axial end whereby a peripheral rim with a relatively small cross sectional radius "r" is formed between the outer peripheral surface of the sleeve section and the outer face of the bottom section.
Bearing bushings are known which have an indentation axially drawn inward in the center of its bottom section which is radially expanded outward in order to form a sharp peripheral rim between the outside surface of the sleeve section and the outside surface of the bore section. A bearing bushing of this type is shown in German Patent application disclosure No. 15 75 502. Since the wall of this known bearing bushing is constructed so that it is offset in the area of the rim, it tends to bend and harmful buckling occurs producing non-uniform material flow during expansion and drawing of the bushing. The construction material is thereby compressed non-uniformly during drawing and expanding of the bearing bushing especially in the area of the peripheral rim so that small cracks are formed in that area which can produce harmful fatigue fissures in operation when using these known bearing bushings, for example, in universal joints. A problem with these prior known bearing bushings, therefore, is that they have a somewhat limited useful life.
In accordance with the present invention, there is provided a thin-walled bearing bushing produced by a drawing process which consists of a cylindrical sleeve section and a bottom section which closes the cylindrical sleeve section on one axial end producing a peripheral rim with a small cross section radius between the outer peripheral surface of the sleeve section and the outer face of the bottom section. The bushing thus produced is formed with a recess radially inwardly which is axially impressed in the outer or inner face of the bottom section near the peripheral rim. A bearing bushing with this construction has a particularly high fatigue strength in spite of the fact that the peripheral rims have a relatively small cross section radius between the sleeve section and the bottom section. Another advantage of this construction is that it can be produced rather economically. Specifically the bushing can be produced by utilizing a drawing ram positioned in the bore and on the inside surface of the bearing bushing. The recess defined inwardly compressed in the outside or inner face of the bottom section is axially pressed with a correspondingly shaped counter ram so that relatively low pressures are needed and the wall of the bearing bushing is formed uniformly without buckling at the periphery.
In accordance with another characteristic or feature of the present invention, the cross sectional radius of the fillet is larger than the cross sectional radius of the peripheral rim so that the construction material of the recess which is radially displaced outward by the counter ram is uniformly and gradually deflected and stretched into the sleeve section. This can be attained according to a further feature of the invention by reason of the fact that the transition of the inside surface of the bottom section to the bore surface of the sleeve section is shaped as a beveled annular surface. The beveled section of the drawing ram which forms this beveled annular surface provides an arrangement wherein the displaced material is pressed into the recess in the counter ram which forms the peripheral rim.
In summary, therefore, a bearing bushing in accordance with the present invention can be produced without harmful buckling or distortion of the wall in a very economical, simple drawing process. The construction material in the area of the rim is uniformly compressed so that an advantageous fatigue strength of the bearing bushing is obtained which also produces a long useful life in supports for highly stressed pins of universal joints. The fatigue strength is further increased by reason of the fact that the recess near the peripheral rim acts as a relief recess for the transmission of axial forces which reduce harmful stress concentration in the area of the peripheral rim of the bearing bushing.